pods

[Aquaria]

so about a month ago i had an outbreak of pods not many amphipods but tons of copapods? i noticed today that i have no copapods and this other type thats iv never seen before, reminds me of the fish eating ones only REALLY small. they have 2 hairs/antenna and i cant see any eyes as there to small.
so what would cause the dieoff of copapods and does anyone know of a site to help id pods since i will not be able to supply a pic lol thx